1. Field of the Invention
The present invention relates to sensors for detecting loads on pins. More particularly, the present invention is directed to sensors for detecting when latches for securing aircraft engine cowls are secured.
2. Description of Related Art
A variety of devices and methods are known in the art for detecting whether an aircraft latch is in a secured state. Of such devices, many are directed to determining whether an aircraft latch for securing an engine cowl is in a secured state.
A typical aircraft 10 having two engines 12 is shown in FIG. 1 with its engine cowls closed. Opening the cowls, e.g. cowl 14 shown in FIG. 2, allows the engines to be serviced and maintained. However, failure to re-secure the cowls after opening them can lead to malfunction of the cowls during take-off or flight. In some circumstances, the cowls can be blown off from the aircraft completely. Fortunately, the loss of an engine cowl is not generally a serious threat to an aircraft. It is nonetheless advantageous to reduce the number of cowl incidents. Typically, the onus is on ground personnel to verify that all engine cowls are secured before an aircraft pulls away from its gate. It is believed that the prevailing cause of engine cowl incidents is failure of ground crew to securely latch engine cowls prior to departure.
Efforts have been made to assist ground crews in verifying engine cowls are secured. U.S. Pat. No. 6,334,588 to Porte describes a system for securing fan cowls in which a maintenance crew can visually detect an unsecured fan cowl because edges of unsecured fan cowls protrude enough to allow for visual detection. Another visual technique for detecting unsecured cowls is described in U.S. Pat. No. 5,518,206 to Arnold et al., which describes an apparatus that extends a flag visible to ground crew when an engine cowl is unsecured.
Other efforts have been made in creating systems to inform operators whether an engine cowl is secured or not by means of sensors. U.S. Patent Application No. 2006/0038410 to Pratt et al. describes a latch having sensors to assist controlling an electrical motor, which operates to open and close a latch for a fan cowl. The sensors can also inform a controller as to the status of the latch.
Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, while visual cues make it easier to verify that an engine cowl is securely latched, these techniques still rely on the ground crew to remember to check the latches. Although solutions to this problem have been developed, such as by using sensors to detect the state of a cowl latch, as in the stress sensors in the latch mechanism disclosed in U.S. Patent Application No. 2004/0012212 to Pratt et al., there still remains a continued need in the art for a latch sensor that is more sensitive, reliable, and easier to change out for replacement. There also remains a need in the art for a system of latch detection that is inexpensive and easy to make and use, including retrofitting existing latches without substantial alterations. The present invention provides a solution for these problems.